A variety of devices have been developed for absorbing the kinetic energy of impact of colliding vehicles, to control the flow and direction of traffic and to identify areas of restricted access for pedestrian or vehicular traffic. Highway barrier devices, for example, have been used in each of the applications noted above. One commonly used highway barrier, formed entirely of pre-cast reinforced concrete, is known as the “New Jersey” style barrier. Highway barriers of this type have a relatively wide base including side walls which extend vertically upwardly from ground level a short distance, then angle inwardly and upwardly to a vertically extending portion connected to the top wall of the barrier. See U.S. Pat. No. 4,059,362.
One problem with highway barriers of the type described above is the high weight of reinforced concrete. A barrier having a typical length of twelve feet weighs about 2,800-3,200 pounds and requires special equipment to load, unload and handle on site. It has been estimated that for some road repairs, up to 40 percent of the total cost is expended on acquiring, delivering and handling concrete barriers. Additionally, concrete barriers have little or no ability to absorb shock upon impact, and have a high friction factor. This increases the damage to vehicles which collide with such barriers, and can lead to serious injuries to passengers of the vehicles.
In an effort to reduce weight, facilitate handling and shipment, and provide improved absorption of impact forces, highway barriers have been designed which are formed of a hollow plastic container filled with water, sand or other ballast material such as disclosed in U.S. Pat. Nos. 4,681,302; 4,773,629; 4,846,306, 5,123,773 and 5,882,140. For example, the '302 patent discloses a barrier comprising a container including a top wall, bottom wall, opposed side walls and opposed end walls interconnected to form a hollow interior which is filled with water or other ballast material, and has fittings for coupling one barrier to another to form a continuous wall. The container structure is formed of a resilient material which is deformable upon impact and capable of resuming its original shape after being struck.
One application of interest for the concrete and plastic barrier devices described above is what is known as a “Type III” barrier used primarily to mount signs which identify areas of restricted access to vehicles or pedestrians, or to otherwise provide indicia of traffic or road conditions. In applications of this type, one or more vertical supports are mounted at the top of the barrier typically by a bracket which rests on the top wall of the barrier and straddles the two side walls. The vertical supports or posts usually mount three vertically spaced panels in position above the top wall of the barrier. A sign is connected to one of the panels in position to be readily viewed by motorists and pedestrians.
It is not uncommon for vehicles to strike “Type III” barriers since they may be placed, for example, in the middle of a road with the sign “Road Closed.” As noted above, concrete highway barriers have little or no ability to absorb the shock of a vehicle impact. In fact, vehicles tend to “ramp up” or move upwardly along a concrete barrier upon impact. If moving fast enough at impact, the vehicle can become airborne thus causing potentially serious injury to the occupants of the vehicle Although plastic highway barriers filled with a ballast material are much more resilient and absorbent to impact shock, they often break apart when struck by a vehicle and allow the sign and/or one or more panels to strike the windshield or other part of the vehicle and penetrate the passenger compartment. This places the vehicle's occupants at risk of injury from flying debris after impact.